Variable resistance.



UNITED STATES PATENT OFFICE.

THEODORE W. CASE, OF BCIPIO, NEW YORK.

VARIABLE nnsrs'rmvcn.

Specification 01 Letters Patent.

No Drawing. Original application filed February 19, 1817, Serial No.149,704. Divided and this application filed May 16, 1917.

To all whom it may. concern:

Be it known that I, THEODORE W. -CASE, a citizen of the United States ofAmerica, and resident of Scipio, in the County of Cayuga, in the Stateof New York, haveinvented new and useful Improvements in VariableRcsistances, of which the following is a full, clear, and exactdescription.

his invention relates to certain improvements in new materials orcompounds showing a variable resistance, and specificallycontemplates amaterial as an element of an electric circuit, subject to the conditionthat variations in light produce a corresponding variation in theelectrical resistance of the element, thereby effecting a change ofcurrent in accordance with variations of light intensity to which theelement is exposed, and is a division'of my copending application,Serial No. 149,704, filed February 19, 1917, which application containsthe claims to a compound of lead, antimony and sulfur for the purposeset forth herein.

The object, therefore, of the invention is the productionof a materialor compound adapted to form a portion of an electric circuit orconductor, the resistance of which diminishes as the intensity of thelight to which it is exposed increases.

I have discovered that a material consisting of or containing lead,antimony and sulfur in varied proportions, or a compound of saidelements, can be utilized as a portion of an electric circuit, and thatits resistance to the passage of currents through said circuit variesunder the influence of light to effect a change of current in accordancewith the intensity of the light rays to which the substance issubjected, and that a material consisting of lead, antimony and sulfuris peculiarly efficient for this purpose and ig'hly sensitive tovariation of light intensity due to the fact that it is practically anon-conductor of electricity in absolute dark and the ratio of change orpercentage change of its resistance to the passage of an electriccurrent under variations of light intensity is very great.

An interesting phenomenon of the invention consists in the fact that theelectrical resistance of the material specified is varied byrays oflight invisible to the human eye, such variation of current beingreadily demonstrated and measured by known appa- Serial No. 189,111.

. any suitable way for contact with each other and exposure to lightrays.

The invention is adapted for and may be applied to various uses, as, forinstance, in 1 the Bell photophone, and I, therefore, desire to broadlyclaim the same without restriction as to the method, manner or conditionof use and without limitation as to the addition of any other elementsto the material or compound so lon as the same do not destroy theutility of t e material for this purpose, and I desire to claim thematerial for use with both direct and alternatin current, and theexpression light rays, as used in the specification and claims hereof isdeemed to mclude both visible and invisible ra s.

What claim is:

1. A resistance element formed of a material containing lead, antimonyand sulfur.

2. An element adapted to var its electrical resistance in accordancewith the intensity of light to which it is exposed, and comprising lead,antimony and sulfur.

3. An electric circuit having a portion supported for exposure to lightrays, such portion formed of a maternal containing lead, antimony andsulfur.

4. A resistance element adapted to be interposed in an electric circuitfor exposure to light rays comprising a series of electrically connectedpieces or a single crystal of material containing lead, antimony andsulfur.

In witness whereof I have hereunto set my hand this 8th day of May 1917.

THEODORE W. CASE.

